Genome rearrangement in top3 mutants of Saccharomyces cerevisiae requires a functional RAD1 excision repair gene.

Saccharomyces cerevisiae cells that are mutated at TOP3, a gene that encodes a protein homologous to bacterial type I topoisomerases, have a variety of defects, including reduced growth rate, altered gene expression, blocked sporulation, and elevated rates of mitotic recombination at several loci. The rate of ectopic recombination between two unlinked, homologous loci, SAM1 and SAM2, is sixfold higher in cells containing a top3 null mutation than in wild-type cells. Mutations in either of the two other known topoisomerase genes in S. cerevisiae, TOP1 and TOP2, do not affect the rate of recombination between the SAM genes. The top3 mutation also changes the distribution of recombination events between the SAM genes, leading to the appearance of novel deletion-insertion events in which conversion tracts extend beyond the coding sequence, replacing the DNA flanking the 3' end of one SAM gene with nonhomologous DNA flanking the 3' end of the other. The effects of the top3 null mutation on recombination are dependent on the presence of an intact RAD1 excision repair gene, because both the rate of SAM ectopic gene conversion and the conversion tract length were reduced in rad1 top3 mutant cells compared with top3 mutants. These results suggest that a RAD1-dependent function is involved in the processing of damaged DNA that results from the loss of Top3 activity, targeting such DNA for repair by recombination.     

Pyruvate is transported by a proton symport inLactobacillus plantarum 8014

Pyruvate is a key metabolic intermediate and the substrate for diacetyl and acetoin synthesis. The mechanism of pyruvate transport was determined inLactobacillus plantarum by use of cells and membrane vesicles. In the cells, protonophores inhibited pyruvate transport, whereas valinomycin did not. Pyruvate was accumulated against a gradient in membrane vesicles. The transport rate and the degree of accumulation increased as the proton gradient increased, but an imposed K potential of –61mV did not drive pyruvate transport. The maximum transport rate (35 nmol/min/mg protein) and accumulation ratio (162-fold) were at pH 3.0, with an apparent Km value of 35 M. These results suggested that pyruvate was transported by a proton symport.     

Tin compounds inhibit the plasma cell response to metallic tin

Injection of metallic tin powder causes intense proliferation of plasma cells in draining lymph nodes of Lewis rats. Pretreatment orally with soluble tin salts prevents this response to subsequently injected metallic tin. In the present work, pretreatment with tin salts by parenteral injection was just as effective as addition to the drinking water. This new approach made the following experiments possible. Poorly soluble tin compounds were found to be inhibitory when injected parenterally. Tin salts injected parenterally into one of two rats joined in parabiotic union prevented the plasma cell response to metallic tin in both parabionts. The transfer of the inhibitory effect via the cross-circulating blood represents significant progress toward understanding the mechanisms involved. The evidence suggests the possibility that tin salts elicit an intermediary substance or process that is responsible for inhibition of the plasma cell response to metallic tin.     

Comparative testing of disinfectant and antiseptic products using proposed European suspension testing methods

The development of standard suspension test methods for disinfectants and antiseptics for adoption in Europe is described. Evaluation of a range of disinfectant agents and products currently used in the UK under conditions as proposed for these tests indicates that the majority of products diluted in water of standard hardness showed satisfactory activity producing a 4·5–5 log reduction in viable count within 5 min against Staphylococcus aureus, Pseudomonas aeruginosa, Enterococcus faecium, Proteus mirabilis and Candida albicans in the absence and presence of 1% albumin. All the products, when diluted with distilled water, produced greater than 5 log reduction in 60 min.     

Decrease in insulin-containing secretory granules and mitochondrial gene expression in mouse pancreatic islets maintained in culture following streptozotocin exposure

We have previously described a preferential reduction in the secretory response to nutrient secretagogues in pancreatic mouse islets maintained in culture after in vitro exposure to streptozotocin (SZ). This reduction was associated with an impaired substrate metabolism at the mitochondrial level. To further clarify this issue, mouse pancreatic islets were exposed in vitro to 2.2 mM SZ for 30 min. At 4 h after SZ treatment ultrastructural changes were apparent in the endoplasmic reticulum and Golgi areas of the B-cells. However, 2 and 6 days following SZ exposure the B-cells appeared well preserved, except for a marked decrease in the number of insulin-containing secretory granules. A morphometric analysis of the B-cells 6 days after SZ exposure showed a normal B-cell size and a normal volume fraction of B-cell mitochondria. However, there was a decrease in total islet size and a 13% decrease in the volume fraction of B-cells in the islets. These mouse islets exhibited a decreased content of the mitochondrial DNA-encoded cytochrome b mRNA, as evaluated by dot-blot analysis. As a whole, the data obtained indicate that SZ treatment does not induce a decrease in the number of mitochondria or long-lasting ultrastructural damage to this organelle. However, there is a clear decrease in the cytochrome b mRNA, suggesting that SZ can induce damage to the mitochondrial DNA.     

Copepoda from deep-sea hydrothermal vents and cold seeps

Recent explorations of hydrothermal vents in the eastern Pacific (Juan de Fuca spreading zone, Guaymas Basin in the Gulf of California, East Pacific Rise at 21° N and 13° N, and Galapagos Rift) and on the Mid-Atlantic Ridge have revealed many copepods, mostly siphonostomatoids with few poecilostomatoids. In these habitats in depths from 1 808 to 3 650 m water temperatures may reach nearly 15 ° C. Among more than 22 000 copepods from vents examined two new families, 11 new genera, and 32 new species were represented.In addition, two new copepods were found in 3 260 m at cold seeps at the base of the West Florida Escarpment in the Gulf of Mexico, an environment not thermally active, with water temperatures about 4.39 °C.Some of these copepods were associated with host invertebrates such as a Nuculana-like protobranch bivalve, a polychaete, and two species of shrimps. Others were obtained from washings of bivalves or vestimentiferans or by means of corers or slurp guns.